Service Discovery with Eureka in Cloud Foundry

A typical cloud application consists of different services that communicate with each other. Because of the cloud’s nature servers come and go and therefore the location of a service (the IP address) will change. Service Discovery allows services to know each other. One way is to set up a service registry where every service can register. Other services can look up the service registry information, get the location and are able to connect to this service directly. A possible implementation of a service registry is Eureka from Netflix.

Spring Boot makes it easy to create stand-alone Spring based applications and with Spring Cloud Netflix it provides an integration of Netflix OSS. In the following I will show a simple setup of a Eureka server with a client in Pivotal Cloud Foundry.

Eureka server

It is really easy to use Eureka with Spring Boot. The first thing you need to start is obviously the server:

Open EurekaApplication.java and add @EnableEurekaServer. It should look like this:

EurekaApplication.java

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@SpringBootApplication

@EnableEurekaServer

publicclassEurekaApplication{

publicstaticvoidmain(String[]args){

SpringApplication.run(EurekaApplication.class,args);

}

}

Add the following lines to application.yml to configure the server: (I prefer YAML, but it is also possible to use application.properties which is provided by the project from the Spring Initializer)

application.yml

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server:

port: 8761

spring:

application:

name: eureka

eureka:

client:

registerWithEureka: false

fetchRegistry: false

The properties registerWithEureka: false and fetchRegistry: false prevent that the application acts as a Eureka client and server at the same time.

Eureka client

The next step is to create an application that registers with the service registry. Go to https://start.spring.io/ and create another application. This time add Eureka Discovery as a dependency:

After importing the project in your IDE, add @EnableEurekaClient in the Main class:

TestAppApplication.java

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@SpringBootApplication

@EnableEurekaClient

publicclassTestAppApplication{

publicstaticvoidmain(String[]args){

SpringApplication.run(TestAppApplication.class,args);

}

}

In application.yml only the application name and the default zone need to be set. The name will be used to register and the defaultZone is the URL of the Eureka server. For a local setup this will be http://127.0.0.1:8761/eureka/.

application.yml

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spring:

application:

name: testApp

eureka:

client:

serviceUrl:

defaultZone: http://127.0.0.1:8761/eureka/

If you start both applications, the logs show that the testApp registers its instance:

Eureka comes with a built-in web UI where it shows all registered services. Go to http://127.0.0.1:8761 to see the registered instance of testApp:

Now that the local setup is running, let’s take it to the cloud!

Cloud setup

The simplest way to deploy an application to Cloud Foundry is to upload the Jar file directly in Cloud Foundry’s web frontend. But this has some disadvantages. The configuration must be done manually and probably the biggest disadvantage: It is not automated!

Congratulations, you have deployed your Eureka server to Cloud Foundry! To verify this, go to http://eureka-test-service.cfapps.io and have a look at the web UI of Eureka.

Adding clients

A service registry without clients is pointless. Therefore the next step is to configure our testApp to use Eureka in the cloud. The easiest way would be to set the default zone to http://eureka-test-service.cfapps.io/eureka/, but this would bind the application to this single instance. If the URL changes you have to recompile the application. Instead of storing environment specific configuration in the application, the environment should provide the URL (see http://12factor.net/config). An easy way to provide the URL via an environment variable is a user provided service.

To enable an application to use a service in Cloud Foundry you have to bind the service to the application.

Cloud profile

If the service is bound to our application it will provide the Eureka URL in the environment variable vcap.services.eureka.credentials.url. To use this in the testApp add a cloud specific spring profile to application.yml and set the defaultZone:

application.yml

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---

spring:

profiles: cloud

eureka:

instance:

nonSecurePort: 80

hostname: ${vcap.application.uris[0]}

client:

service-url:

defaultZone: ${vcap.services.eureka.credentials.url}

The hostname is set to vcap.application.uris[0]. This variable is provided by Cloud Foundry and contains the public URL of an application. This URL will be used to register with Eureka. Other services can then retrieve this URL from Eureka to connect to testApp.

Manifest

Just as the server project has a manifest.yml, so the testApp will have one:

The active spring profile is selected with the environment variable spring.profiles.active: cloud which can be set in the env attribute.

The service eureka is bound to this application in the services block.

The complete manifest.yml should look like this:

manifest.yml

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---

applications:

- name: testApp

memory: 512MB

host: testApp-service

path: target/testApp-0.0.1-SNAPSHOT.jar

env:

spring.profiles.active: cloud

services:

-eureka

Deploy it to Cloud Foundry

As usual first build the jar: mvn clean install

Now push it to Cloud Foundry via CLI: cf push

The logs show the registration of the Eureka client with the Eureka server.

On the UI http://eureka-test-service.cfapps.io you can see that TESTAPP is registered.

That’s it! Within a few simple steps you have created a service registry with Spring Boot. First a Eureka server and client for a local setup, then configured both to be cloud ready and deployed them to Cloud Foundry.

With the default configuration Zuul will fetch the services from Eureka and map the service to an URL, e.g. testApp will be reachable under /testApp. The service name is the name of your application configured via “applications.name”.

I’m sorry I couldn’t give you an exact answer, but I hope the information helps you.

22. August 2018 |

Vinay

Hi, I registered my client in the server. It is showing up too. But it is always appending a port number(8080) with the pcf route for that particular client. Hence it cannot call other clients registered in the same eureka. Without the port number the urls are working perfectly. Any suggestions on how to resolve this.

22. August 2018 |

Vinay

Just check if you are missing /eureka at the end of default zone url. I did the same mistake 😛

22. August 2018 |

Poonam

Hi Johannes,

The post is very useful and i get it done on my machine too.However I got stuck in zuul configurations in cloud.Please refer a post regarding configuring Zuul on Cloud foundry.’

Specifically How to get the service id of services registered in Eureka

06. August 2018 |

sajal jain

I am following the same procedure to deploy Eureka server and Eureka client on PCF cloud. My eureka server has been successfully deployed but when i push eureka client it fails with the error “Could not find service eureka to bind to testApp “. i am not able understand why ?
Can someone please help?

29. June 2018 |

Johannes Dilli

Our defaultZones are different: You added /eureka.
How did you create the user provided service? What is the value of vcap.services.eureka.credentials.uri?

If you created the user provided service with ‘http://eureka-test-service.cfapps.io/eureka/’, your defaultZone will be ‘http://eureka-test-service.cfapps.io/eureka/eureka’ and that will cause an error.

John

I’m getting a ClientHandlerException: java.net.ConnectException: Connection refused when the client attempts to contact eureka on CF. Should I be creating an application security group?

13. September 2016 |

John

Oh I see. Thanks!

How would the application.yml look for Eureka if you were to set it up for peer to peer for Cloud Foundry

09. September 2016 |

Johannes Dilli

In the cloud setup application.yml I extend the application.yml from the local setup. The first defaultZone is used with the default profile and the second with the cloud profile. So you are still able to run and test the application on your local computer. If you prefer to remove the defaultZone http://127.0.0.1:8761/eureka/, local testing becomes more difficult.

09. September 2016 |

John

In the cloud setup application.yml you have defaulZone twice http://127.0.0.1:8761/eureka/ being the first one. Shouldn’t this be removed, and only contain the following?